Rinse lentils; place in a small saucepan with the water. Bring to boiling; reduce heat. Cover and simmer for 20 to 25 minutes or just until tender. Drain and chill for 1 to 2 hours or until thoroughly chilled.
Arrange the tomatoes, cheeses, spinach, cooked lentils, and prosciutto or ham on a large serving platter or in a serving dish.
For dressing, in a screw-top jar combine vinegar, olive oil, lemon juice, mustard, rosemary, salt, and pepper. Cover and shake well. Drizzle over salad. Makes 8 to 10 servings.